Measuring Earthquakes

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vocabulary

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focus:the part where the earthquake starts
epicenter:the surface above the focus
seismic waves:the waves that come out of the focus
p waves:the waves that that squeeze the land together
s waves:the waves that expand the land
surface waves:that waves tat travel on the surface
seismograph:this instrument measure that vibration of the waves
magnitude:the measure of seismic waves
mercalli scale:the scale that measures earthquake by their intensity
richter scale:it rates the size if the seismic waves
moment magnitude scale:it tell how much energy was let out during the earthquake

outline

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seismic waves

• there are different types of seismic waves
• primary waves, secondary waves and surface waves
  • surface waves move slower then s and p waves
    • p waves go up and down
  • s waves go side to side

Primary Waves

(P Waves)

• the first type of waves to arrive is P Waves
• P waves can cause structures to contract and expand
  • P waves can travel through liquids and solids

Secondary Waves

(S Waves)

• after P waves, S waves come next
• S waves reach top of the grond and the shake the building above the ground violently
  • not like P waves the S waves can't travel through liquids

Surface Waves

• surface waves happen when p waves and s waves reach the surface
  • some of the P waves and S waves turn into surface waves
• surfaces waves moves slowly compared to P waves and S waves
• some surface waves looks lke ocean waves for sometimes they make the ground roll

Detecting Seismic Waves

• to take data from the vibrations of seismic waves, geologists use tools called seismographs
• before they made electronic seismographs they made mechanical seismographs
  • mechanical seismographs has a heavy weight attached o a frame by a spring or wire
    • then they put a writing material usually a pen connected to the weigh then rests its point on the paper on the rotating drum
  • it will draw straight and when it zig zags on the paper that shows you how big or how small the waves were

Measuring Earthquakes

• there are about 20 different type of ways to measure earthquakes and those 20 types of ways are all different some with its strengths and some with with their own disadvantages
• there are three ways of measuring earthquakes so far and they're the mercalli scale, Richter scale, and the moment magnitude scale

The Mercalli Scale

• the Mercalli scale was developed in the twenieth century
  • the Mercalli scale was made to rate the earthquakes that happened
• Mercalli scales aren't the exact measurement
  • but it tells you how it affects structures,buildings, and land surfaces

The Richter Scale

• the richter scale was developed somewhere in the 1930s
• Geologists had used this instrument for about 50 years
  • but soon after electronic seismographs replaced the mechanical seismographs that are used for the richter scales
• The richter scale was used for small nearby earthquakes not large or far away earthquakes

The Moment Magnitude Scale

• geologists still use this today
• to rate earthquakes on moment magnitude scale geologists have to first study data from the electronic morden seismographs
  • The data may show what kinds of seismic waves the earthquake had made and how strong they were
• Geologists must combine all the information that have to rate it on the moment magnitude scale
  • Earthquake's magnitude that is below 5.0 cause little damage and the one above 5.0 cause alot of damage

Locating the Epicenter

• Geologists use seismic waves to find the earthquakes epicenter
  • seismic waves all travel at different speeds
• farther away an earthquake is, the time is different between the happenings of the S waves and the P waves
• Geologists usually always draw at least 3 circles using the data from different types of seismographs